Does Blender have a "distribute evenly" function?
You could add a Copy Location constraint to each of the intermediate objects (with each of them initially positioned at the same point as the original) with the 'target' set to the last object, and then adjust the constraint Influence appropriately - ie, 0.25, 0.5, 0.75. This will distribute the intermediate objects at the correct spacing between the original and the last.

You could do the same with a Copy Rotation and Copy Scale constraint to have the intermediate objects similarly blend those attributes. Changing the Location, Rotation, or Scale of the 'final' object would then cause the intermediate ones to automatically move, rotate, and scale to blend to the final location/rotation/scale.